I had answered this in a similar thread, but the short answer to me is they are very useful, as long as you are aware of the pitfalls and you have an instructor that is also aware of them or familiar with what FS can and can not do.
Mine actually tried out my sim rig at one point just to feel the difference first hand. But not every CFI will be inclined to do this sort extra curricular activity.
Lastly, as great as MSFS is visually and in some ways at least physically, the old versions I found a lot easier to fine tune aircraft to match a real world counterpart. Nowadays I am not sure I could tweak a PA28-161 or 181 to be a virtual twin to the real one.